Process for the concentration of isotopes



Nbv. 23, 1954 c. A. H. wmen-rr 2,695,268

PROCESS FOR THE CONCEN TRATION 0F ISOTOPES Filed Jan. 27, 1945 2 Sheets-Sheet l Q F! G. a 2 Char/ es A. H. W/"(ghf (lithe meg Nov. 23, 1954 3, H, wm 2,695,268

PROCESS FOR THE CONCENTRATION OF ISOTOPES Filed Jan. 27, 1945 2 Sheets-Shut 2 WATER AND DEUTERIUM OXIDE CONTAINING CAUSTIC ELECTROLYTIC CELL GASEOUS HYDROGEN, DEUTERIUM AND OXYGEN AND SPRAY AND VAPOUR OF WATER AND DEUTERIUM OXIDE DRYING VESSEL CONTAINING CAUSTIC SOLUTION OF CAUSTIC IN MIXTURE OF WATER AND DEUTERIUM OXIDE CONTAINING A RELATIVELY LARGE AMOUNT OF DEUTERIUM OXIDE GASEOUS HYDROGEN, DEUTERIUM AND OXYGEN COMBUSTION BURNERS ELECTROLYTIC CELL CONTAINING ELECTROLYTE OF LIKE ISOTOPIC COMPOSITION MIXTURE OF WATER AND DEUTERIUM OXIDE CONTAINING A RELATIVELY SMALL AMOUNT OF DEUTERIUM OXIDE ELECTROLYTIC CELL CONTAINING ELECTROLYTE OF LIKE ISOTOPIC COMPOSITION PIC-3.2

INVENT OR CHARLES AH. WRIGHT United States Patent ()fifice PROCESS FOR THE CONCENTRATION OF ISOTOPES Charles Alfred Holstead Wright, Tadanac, British Columhia, Canada, assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application January 27, 1945, Serial No.

1 Claim. (Cl. 204-101) successive stages, the elecstage containing a higher concentration of heavier isotopes than the electrolyte in the imme- In this manner, as lectrolysls isotopes in each case is liberated as gas. in this type of process, it has been lect and burn these liberated gases to For this reason, the practice to coless as feed water to an earlier stage.

In the operation of this type of process,

isotopes in the spray and vapour, on being again subjected Spray traps of various kinds have been used with a view to recovering part of the spray 2,695,268 Patented Nov. 23, 1954 has been found ditficult to recover the spray collected by the sand.

I have discovered a method which enables a much omy in the process.

I have found that the spray and vapour may be satisfactorily removed from the gases leaving the electrolytic cells by causing the gases containing the spray and vapour to pass through a vessel charged with small lumps of caustic potash or caustic soda, depending with the spray and vapour, during electrolysis of each batch of electrolyte.

T e caustic solution collected in this manner in the concentration.

The effectiveness of the steel wool were usedinstead in the gas stream under similar conditreatment with resulting losses in product and in economy. After a run of this duration when operating under these conditions, the drying vessel is customarily replenished by adding a charge of about 75 lbs. of solid caustic potash prior to the next run.

A suitable design of enclosed drying vessel is shown in the accompanying drawing. The vessel, which may be of iron, comprises an outer gas-tight shell 1, the side walls of which may conveniently be cylindrical, fitted with a permanent bottom 2 and with a removable cover lid 3 containing a centrally located outlet 4 for gas. There is supported inside the shell a cylindrical basket 5 of which the side wall is gas-tight, but the bottom is a perforated plate 6. The top of the basket 5 is open, but is so located within the shell 1 that its upper edge is flush with the tlat cover lid or bolted in place. cal shape, is located near the top of the basket 5 and just below the centrally located outlet 4 in the cover lid 3. The baffle 7 is supported by legs 8 fastened to a plate 9 which, in turn, is supported by a ring 11) welded around the inside of the basket 5. Holes are provided in the plate 9 to permit passage of the gas. The side wall of the shell 1 is fitted with an inlet 11 for gas near the top, and with an outlet 12 for drainage solution near the base of the shell. The cover lid 3 is clamped or bolted in place and is readily removable for recharging the vessel with the drying agent. The baffle 7 together with the plate 9 can be easily lifted from the ring to facilitate recharging of the vessel.

In operation, the gas with its burden of aqueous spray and vapour evolved from the electrolytic cells is led into the vessel through the inlet 11 and is passed down around the cylindrical basket 5, and then up through the perforated plate 6 on which is supported the charge of caustic lumps 13.

The gas, with its burden of spray and water vapour, passes up between, around, and in contact with the lumps of caustic, and, before leaving the vessel through the outlet 4 in the cover lid, the gas in a dried condition is deflected around the baffle 7 placed directly beneath the outlet 4.

The caustic solution, formed by dissolution of the lumps of caustic 13 in the spray and water vapour carried by the gas, is allowed to trickle down to the base is collected to a suitable depth outlet 12.

It is preferable to pass of drying agent to the flow of aqueous solution of the drying agent which trickles off the lumps, so that the gas on leaving the drying vessel is in contact with relatively dry lumps of the drying agent. It may be desirable, however, to use two or more drying vessels in series, and in this case the gas may be passed down with the flow of aqueous solution, suitable provision being made in the design of the vessel to accommodate the flow of gas in this case.

Where countercurrent flow of gas and solution is employed in the drying vessel, it is preferable to employ in the drying vessel a basket designed to hold a column 0 the drying agent such that the dimensions of the column will permit the velocityof the gas in an upward direction enough to permit the droplets of solution to vessel without being carried up and Where the hydrogen gas and the oxygen gas generated in the cells are kept separate in the cells and are evolved separately, each gas may be passed through a separate drying vessel and the resulting aqueous solutions of the drying agent may be returned to the appropriate stage as described herein.

My improved method offers the advantage that the aqueous spray and vapour are collected in a form suitable for feeding directly to the cells and no separation through the first drying vessel concurrently of the collected water from the drying agent is required, as would be the case and with additional expense were silica gel, or phosphoric anhydride (P205), or other drying agents employed. In the practice of the present invention, when, as a result of the drying action the lump caustic is exhausted as regards effectiveness as a drying agent, the caustic solution resulting from the drying is itself subsequently utilized to good advantage in the electrolytic process and serves to supply conducting agent needed for electrolysis of the water. Furthermore, as the caustic dissolves in the moisture removed from the gas mixture, the caustic solution drains off the lumps, leaving these lumps with a freshly exposed surface to dry further quantites of gas, whereas other types of drying agents would become progressively more saturated with water and accordingly less effective as drying g nts.

This method is definitely superior to that employing spray traps, as such traps serve merely to remove some of the spray, bu is a considerably greater than weight of moisture carried as vapour as spray under normal operating conditions in this type of process. When sand traps are used in the system, the tendency of these to become plugged with solid caustic from the spray from the caustic electrolyte when spray traps are used, is largely avoided by placing caustic drying vessels, instead of spray traps, ahead of the sand traps.

This improvement is of particular value where the electrolysis is conducted in cells operated by the batch method and where these cells are used in the final stages of the concentrating process, in which high concenrtations of the heavier isotopes, for example, deuterium, are being treated.

I claim:

In a process for concentrating deuterium oxide in a caustic electrolyte consisting of caustic dissolved in feed water by electrolytic fractionation in successive stages of progressively higher deuterium content in which the major portion is of the electrolyte in each stage electrolytically decomposed to a gaseous mixture of hydrogen, deuterium and oxygen carrying water in liquid and vapor phase form containing deuterium'oxide, until the deuterium content of the gaseous mixture from each stage approximates the deuterium content of the feed water to that stage, the improvement which comprises drying the gaseous mixture generated during electrolysis in each stage by contacting said gaseous mixture with solid caustic drying agent to form an aqueous solution of the drying agent and adding said solution to a stage wherein the electrolyte contains a concentration of deuterium oxide approximately equivalent to that of the solution.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,044,704 Knowles June 16, 1936 2,137,430 Webb Nov. 22, 1938 OTHER REFERENCES Journal of Chemical Physics, December 1933, vol. 1, pp. 823 and 824, an article by Taylor et al.

Zeitschrift fiir Electrochemie, vol. 40 (1934), pp. 298, 299, an article by Schwarz et al.

J. Soc. Chem. Ind, pp. 355, 356, vol. 38 (1919), an article by L. D. Williams.

Johnston: 1. A. C. 8., vol. #57, March 1935, pp. 484486.

Taylor et al.: Theoretical and Practical Studies of Atomic and Molecular Forms of the Hydrogen Isot(opes,; Proc. Am. Philosoph. Soc., vol. 72, pp. 255-263 

